1. Field of the Invention
The present invention relates to a technology field of printing apparatuses for carrying out printing on sheets.
2. Description of the Related Art
An ink-jet printing apparatus discussed in U.S. Pat. No. 7,395,778, is provided with a coating mechanism for applying a coating liquid (pre-treatment liquid) that reacts with ink color materials, on sheets in advance before printing operation. The coating mechanism includes a coating roller having a coating surface for applying the coating liquid on a sheet, and a liquid holding member that abuts on the coating surface of the coating roller so as to form a liquid holding space in which the coating liquid is held. The coating mechanism is used to apply the coating liquid on the sheet while conveying the sheet by rotating the coating roller.
If an operation is stopped while the coating roller and the sheet are in contact with each other during the coating operation, the coating liquid spreads not only over the contacting portion of the sheet, but also over a surrounding area of the contacting portion, and as a result a large amount of the liquid is absorbed into the sheet, thereby causing an uneven coating, in which the coating liquid is not uniformly applied. If uneven coating becomes locally conspicuous, a uniform print quality on the sheet cannot be guaranteed. In an apparatus discussed in U.S. Pat. No. 7,395,778, a length of a sheet conveying path from a coating mechanism to a print start position is made sufficiently longer than a sheet length in a conveying direction so that the coating operation can be carried out without interruption. However, relatively long distance is used for the conveying path from sheet feeding to printing, accordingly relatively long time is consumed from the sheet feeding to the print start.
In order to enhance a total throughput when continuously printing a plurality of pages or sheets, a distance of the conveying path used for the sheet feeding is shortened, thereby a time (blank time of printing) consumed from completion of printing of a certain page to a start of printing of a next page is reduced as much as possible.